1. Field of the Invention
The present invention relates to a radio communication system composed of a portable device such as a portable telephone or a portable information terminal and its radio accessory such as a radio hands-free device, and in particular to a radio communication system and method between them.
2. Description of the Related Art
There has been commercially available a radio hands-free device provided for a cellular phone, allowing hands-free telephone conversation.
On the other hand, there has been standardized short-range radio communication such as Bluetooth™ that is an open standard for short-range transmission of digital voice and data between mobile devices and desktop devices. Such a short-range radio interface is expected to connect a cellular phone to a peripheral device and various accessories or peripheral devices allowing connection to the cellular phone by the short-range radio interface are researched and developed. As such an accessory or peripheral device, a hands-free device, a wristwatch-sized keypad device or the like can be considered.
In addition, such an accessory is allowed to control the cellular phone without directly operating it. Since the accessory is smaller and lighter than the cellular phone, the user can use it to operate the cellular phone that is taken in his/her bag or the like as a so-called base station.